1. Field of Invention
The present invention relates to a color filter. More particularly, the present invention relates to the black matrix of a color filter.
2. Description of Related Art
Improved driving techniques have made it possible to create a low power consumption, thin, light-weight liquid crystal display (LCD) that works under a relatively low driving voltage. This allows LCDs be broadly used in consumer electronics including home appliances, computers, and projectors . An ordinary thin-film-transistor LCD (TFT-LCD) includes a TFT array substrate, a color filter substrate, and a liquid crystal layer filled between two transparent substrates. The TFT array substrate further includes thin-film transistors, word lines, bit lines, and pixel electrodes. The color filter substrate includes a black matrix, and a color filter. The TFT array substrate and color filter substrate are first aligned and then attached together. After they are aligned, the black matrix of the color filter substrate is placed above the transistors, word lines and bit lines to prevent light leakage therefrom.
Since the purpose of forming a black matrix, which is used as a light shield layer, on the color filter substrate is to prevent light leakage, the black matrix must have good light-blocking characteristics, and a low reflectance. Currently, the most commonly chosen materials for forming a black matrix are either metals (such as chromium Cr), or resins. Chromium provides an excellent light shield layer. However, its metallic surface cannot alone meet the requirement of low reflectance. In order to lower the reflectance, a multi-film method is usually applied, so that the interference caused by the Cr films will reduce the reflection. This conventional multi-film process increases the complexity of manufacturing process, and still cannot provide a satisfactory low reflectance for all frequencies of visible light.
Opposingly resin has a low reflectance for all visible lights, and is made by a manufacturing process similar to the later process for making a color filter layer. However, resin cannot provide an effective light shield layer. For example, in order to have the same light shielding of a 0.1-micrometer Cr layer, the resin layer has to be made 1.2 to 1.5 micrometers thick. As a result, a black matrix of such a thickness will cause a very uneven top profile on the color filter.
According to the foregoing, conventional black matrixes, either made of metals or resins, have drawbacks. Black matrixes made of metals cannot provide low reflectance, even one made by applying multi-film process still cannot provide a satisfactory reflectance for the entire visible range. The excessive thickness of a resin black matrix causes difficulty for later manufacturing processes.
Accordingly, one object of the present invention is to provide a black matrix for a color filter to reduce the thickness thereof, as well as to lower the reflectance.
A second object of this invention is to provide a method of manufacturing a color filter to reduce reflectance without having an overly-thick black matrix or complicated multi-film process.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a color filter substrate including a transparent substrate, a black matrix, a color filter layer and a transparent common electrode. The black matrix is formed on the substrate, and distributed on partial surface of the substrate, wherein the black matrix further includes a resin layer and a light shield layer for both lowering the reflectance and improving the light shielding capability. In addition, the black matrix of the invention is much thinner than a conventional resin black matrix. The color filter layer is formed on the top surface of the substrate that is not covered by the black matrix. The common electrode is formed on top of the color filter layer, and the black matrix.
The method of the invention begins with forming a black matrix on a color filter substrate, wherein the black matrix includes a resin layer and a light shield layer. A color filter layer including red, green and blue photoresists is next formed on the substrate and filled into the space of the black matrix, and then a transparent common electrode is formed on the black matrix, and color filter.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.